Flying cutoffs for tubing, roll-formed shapes and the like, typically comprise a die mechanism mounted on slides and powered by an accelerator for travel synchronously with and in the direction of the moving work. In addition, a separate power source such as a mechanical press is provided for actuating the die through the work stroke to sever the workpiece. See, for example, U.S. Pat. No. 3,288,011 issued Nov. 29, 1966 to Alexander Borzym.
Efforts have been made to combine the acceleration and work stroke functions so that they can be powered by a single source. One effort, believed to have been undertaken by Kusakabe of Japan, involves the use of a rotary power source and a crank on the end of the rotary power source output shaft. The circular-sweeping end of the crank is pivotally connected to the upper platen of a cutoff die set such that when the crank is rotated, the die set is caused not only to move with the work but is also opened and closed.
A substantial problem of stability and excessive work stroke results from the device just described. For example, assuming the crank is approximately 14 inches in length, the horizontal travel of the die set with the work is approximately 28 inches but the vertical travel of the upper platen in the work stroke direction is also 28 inches. This is substantially more work stroke travel than is actually required to cut tubing or the like and results in the necessity for die set construction which accomodates the excess work stroke and which provides stability over the entirety of this stroke.